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I just read an article on the site stating that excessive cardio is damaging to your health. Overall I think this is probably correct and makes sense to me. In that article, Mark compares the body of a typical marathon runner to the typical sprinter. I think that he used two extreme examples to illustrate a point. However, I have a specific case I want to bring up. A man named Dean Karnazes. He is "ultramarathon" runner. And yet when you look at images of him, he doesn&#39;t fit that stereotype that Mark brought up. I read an article on him a few years ago in Wired magazine, and he doesn&#39;t just do excessive cardio, he does ultra excessive, to the point of his feet bleeding from blisters. And yet his body looks like it has plenty of lean muscle mass.

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This interview touches on Dean&#39;s training, and of course there are his books.

He runs less than many ultrarunners (though 70-80 miles a week is still solid by anyone&#39;s count). He also does a lot of other outdoor activities like windsurfing. When he&#39;s not actually running his diet is very different from the traditional runner&#39;s CW diet (and has some similarities to PB). That said he eats like a pig while competing.

So, if Mark Sisson&#39;s right (as I think he is) that 70-80% of body composition is diet-related, Dean&#39;s diet is probably mostly responsible for his look. It&#39;s also worth noting that that picture makes him look a lot bigger than he really is.

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Well, there may be underlying wear-and-tear on his body that won&#39;t show up for another few years yet. The evidence of how supportive of health, functional fitness, and longevity ISN&#39;T IN HOW RIPPED A BODY is. There is even some science to suggest that a small amount of fat on a body is healthier than being extremely lean.

There is a difference between PEAK FITNESS and health. If I could draw a graph with increasing fitness on the X axis, and increasing health on the Y axis, you could see that there is a point out the X axis that the Y axis starts to go down----that point of peak fitness beyond which just a little more causes breakdown, overtraining, injury, and illness.

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Should have posted this in my reply, but I just remembered it now. Don&#39;t discount the fact that Dean Karnazes is probably a statistical outlier. He&#39;s almost certainly an exception to the general rule.

Just because Karno can go ultrarunning and maintain some muscle mass (or that Scott Jurek can do it as a vegan ultrarunner) doesn&#39;t mean it would work for most of us.

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Geoff, I think that&#39;s probably true. What&#39;s interesting to me is that in reading Elizabeth Marshall Thomas&#39; accounts of living with the !Kung bushmen when they were still hunter-gatherers, she notes that only ONE hunter in the community did the run-&#39;em-till-they-drop type hunts. (I think they are called "persistence hunts" in which a hunter walks and runs an injured animal for as long as 3 or 4 days.) It was something of a specialty, perhaps rather like Dean K.&#39;s.